The present invention relates to touch fasteners in general, and more specifically, to touch fasteners with metal constituents. The touch fasteners may be used for incorporation by molding into molded articles, or as part of systems requiring electromagnetic field shielding, or grounding.
Hook and loop type separable touch fasteners, such as those sold under the trademark Velcro.RTM., are well-known and are used to join two members detachably to each other. This type of fastener has two components. Each has a flexible base material having one component of the fastening system on a fastening surface thereof. One component is typically comprised of resilient hooks while the other is comprised of loops, and when the two surfaces are pressed together they interlock to form a releasable engagement.
Separable fasteners are used in the manufacture of automobile seats in the attachment of an upholstered seat cover to a polyurethane foam bun. One portion of the separable fastener is incorporated onto the surface of the polyurethane foam bun during the foam molding process. The mating portion of the separable fastener is attached to the seat cover to provide releasable attachment to the foam bun. The separable fastener assembly used in the foam mold for incorporation in the bun surface typically comprises the hooked portion of a separable fastener. This hook portion is characterized by a base carrying resilient hooks on a fastening surface. The opposite, non-fastening surface of the base may carry anchor projections to become incorporated into the foam to provide stable attachment of the separable fastener assembly to the foam article. It is also common for a backing layer or substrate to mate with the non-fastening face of the base. The substrate may be of a material that is more conducive to handling of the component or its adherence to other articles. Alternatively, the backing layer may be looped fabric, to which the foam material adheres well. Anchor projections may also project from the substrate. Further, other components can be sandwiched between the substrate and the base.
A protective layer, such as a thin plastic film, may be placed over the resilient hooks, to prevent incursion of foam into the hooks during the molding process, since significant foam contamination of the hooks would affect their ability to engage with the mating portion of the fastener attached to the seat cover. Alternatively, an elastomeric cover that intimately surrounds the hooks, except for a small portion at their tips, can also be used. After the molded article is fabricated and removed from the mold, the elastomeric material is removed.
In some assemblies, a magnetically attractive solid metal shim is attached to the base to facilitate placement of the assembly in a valley (also known as a trench or trough) or on a pedestal in the mold cavity wall, which is equipped with magnets. The shim helps secure the hook-carrying face of the component tightly against the mold wall, thereby further minimizing incursion of the foam into the hooks. The assemblies may be referred to as "mold-in" fasteners or assemblies, due to their use in such molded products.
The solid shim can be incorporated into different locations in the assembly. It can be sandwiched between the hook carrying base and a substrate or backing layer, either temporary or permanent. It can be located centrally relative to the width of the hook-carrying base, or along its marginal edges. In cases where a thin plastic film is used to cover the hooks, the solid shim can be sandwiched between the plastic sheet and the hooks.
As mentioned above, it is also known to substantially cover the hook region with an elastomeric material that protects the hooks against incursion of the foam. It is known to include a magnetic attractant in this elastomeric material.
Known methods of adhering the protective film cover to the hook-carrying component include to use a long bead of hot melt adhesive there between. It is also known to include a magnetic attractant in this hot melt material.
The known methods all have drawbacks. With regard to the solid metal shim itself, it presents an extra component and an extra manufacturing step, thereby contributing to the cost of the assembly and the time for manufacturing a given length of material. The solid metal shim also contributes to the weight of the material. In the construction process, care must be taken that workers are not cut by the solid metal strips. The solid metal limits the flexibility of the strip, and consideration must be taken of the thermal expansion and contraction properties of the various binders and additional layers that might be used to secure the strip to the substrate. It is also often difficult to adhere the solid metal shim to the fastener material or to a separate backing layer, requiring adhesives or other methods.
Considering those known assemblies that use either the protective plastic or the elastomeric cover to contain the solid metal shim, or a magnetic attractant, there are reasons to eliminate these protective covers, if possible. The protective covers also entail additional steps, in their manufacture, attachment to the fastener assembly, and removal from the fastener assembly after molding. All protective material must be removed from the hooks (or loops, if it be the loop carrying component molded into the article), or else the hooks (or loops) will not be exposed to fasten to the mating component. These extra steps must typically be conducted away from a normal high speed production line and contribute to the cost of the fastener assembly, the time for its manufacture, and also generate a relatively large volume of essentially waste material. Additionally, sometimes a residue from the cover material remains on the fastening component after removal, which is undesirable.
When a solid metal shim is used between the base and the foam, some means must be had to secure the shim to the base and the base plus shim assembly to the backing layer or foam, if no backing layer is used. Such means include adhesives, which also entail extra steps, expense, and complications.
Use of a separate substrate for anchoring or securing the fastening component to a foam product, if that is to be its use, also has undesirable effects. It requires an additional piece to be used, contributing to the cost, weight, expense and time involved in making the part. It also increases the inventory that must be kept on hand for manufacturing purposes, and the amount of machinery required to manufacture the components.
Thus, there is a great need for a touch fastener assembly that can be molded into a molded product, without the use of solid metal shims or protective covering for the fastener components. There is also a need to simplify the manufacture of such mold-in assemblies, to minimize their cost, production time, and the time to prepare the molded product for use. It is thus an object of the invention to facilitate a simple means for providing a magnetic attractability to the mold-in fastener assembly. It is another object of the invention to provide a light weight mold-in assembly that does not require a solid metal shim or protective covering for the fastener components, such as hooks. It is another object of the invention to easily attach the base of a fastener component to an anchoring backing layer, while also providing a magnetic attractability. Yet another object of the invention is to provide a magnetic attractability, and also to facilitate securing the fastening component to an article being molded, without using a separate substrate or anchor layer.
In addition to the uses described above, fastener products are also useful in situations where electromagnetic shielding, or grounding or interaction of some sort is required. For instance, it may be advantageous to include a grounding component in separable fastener strips that are used cable ties to secure a bundle of electrical cables together or to fixtures. Further, airplanes typically have areas on the wings or bodies that are covered with an expanded metal sheet, to act as a lightning strike and dissipater. These sheets are typically attached using epoxy or adhesives, and are essentially permanent once attached. It may be desirable to provide such a lightning strike that is selectively removable, such as using a separable fastener.
The important feature of these products is that they contain an electrically conductive metal phase distributed throughout the region over which the product is deployed, and that the component be removable in a non-destructive, relatively simple manner.
Thus, there is also a need for a fastener product that contains an electrically conductive metal phase, which is flexible and lightweight and easily attachable and detachable from a body without destroying the body and without requiring adhesives.